For inkjet printing apparatuses, a so-called tank exchange scheme has been proposed in consideration of the convenience and cost effectiveness for apparatus users. In this scheme, ink tanks that store ink for inkjet printing can independently be set for a printhead. When the ink is running out, only the ink tank is exchanged.
On the other hand, conventionally, the printhead can easily be detached/attached to/from the printing apparatus main body so that the apparatus user can easily exchange the printhead with a new one in case of failure in the printhead. In inkjet printing apparatuses which are relatively expensive and have large apparatus volumes, and inkjet printheads and ink tanks used for these apparatuses, the ink tank has electrical or optical elements (parts). The ink-jet printing apparatuses have reading elements for the electrical or optical elements.
In an inkjet printing apparatus having the above-described arrangement, the reading elements and reading function are mainly used for ink level detection. They are not used to detect the presence/absence of the ink tank itself. Even when no ink tank is attached at all, control for cleaning is sometimes executed as in an ink tank attached state.
In inkjet printing apparatuses which are relatively inexpensive and have small apparatus volumes, and inkjet printheads and ink tanks used for these apparatuses, there can be neither special detection elements nor a detection function to detect the presence/absence of the ink tank. Exchange or attachment/detachment of the ink tank is estimated by determining conditions such as the open time of the front cover of the inkjet printing apparatus. In this case, the presence/absence of the ink tank cannot directly be detected. Even when no ink tank is attached at all, control for cleaning is executed as in an ink tank attached state.
Even in inkjet printing apparatuses which have a mechanical detection function of detecting the presence/absence of the ink tank, the same control for cleaning as in an ink tank attached state is executed even when no ink tank is attached at all.
In Japanese Patent Laid-Open No. 9-11492 or 8-039830 (which corresponds to U.S. Pat. No. 6,447,095), the presence/absence of the ink tank is detected to prevent the ink from hardening in the inkjet printhead when the apparatus is left for a long time in an ink tank unattached state. Especially, control has been proposed, in which when no ink tank is attached, ink is completely discharged from the ink channel in the inkjet printhead by using a recovery mechanism such as a suction mechanism or ink predischarge mechanism.
However, in the conventional inkjet printing apparatus, as described above, the same cleaning operation is performed independently of the presence/absence of the ink tank. When the ink tank is detached because ink in it is completely consumed, the ink level in the inkjet printhead is also already zero or almost zero.
In this state, the same cleaning sequence as in the ink tank attached state, i.e., a cleaning operation such as an ink predischarge operation, wiping operation, or ink suction operations is executed. Particularly, in the ink predischarge operation, ink discharge energy generation elements are energized although there is no ink. In this case, the energy generation elements are damaged and adversely affect the normal ink discharge performance, as is known.
Similarly, when the wiping operation is executed, the wiping member abuts against the face surface of the inkjet printhead with ink discharge nozzles and slides although the ink level is almost zero. This may degrade the water repellency of the face surface of the inkjet printhead and decrease the reliability of ink discharge.
In addition, since a color other than a predetermined color is pushed into the inkjet printhead by the wiping operation, and the above-described ink predischarge operation is insufficiently executed, a problem such as color mixing is posed by the residual colors other than the predetermined color.
The ink suction operation itself does not damage the inkjet printhead. However, when the ink suction operation is executed, the inkjet printhead receives the same damage as described above because of the wiping operation and ink predischarge operation, which are included in the series of cleaning operations in ink suction.
When ink is discharged from the inkjet printhead in the ink tank unattached state, as in Japanese Patent Laid-Open No. 9-11492 or 8-039830, clogging in the ink channel of the inkjet printhead by ink remaining in it can be prevented. However, as the resolution and image quality of inkjet printing apparatuses are recently becoming higher, the discharge amount of the ink-jet printhead is decreasing. To realize such a small ink discharge amount, the ink discharge nozzle area must be reduced. In small ink discharge nozzles, a hardening substance is generated near them by a small amount of ink that remains when the ink in the inkjet printhead is discharged. This adversely affects ink discharge.